The demand for mobile data and voice communication continues to evidence significant growth. Examples for mobile communication systems include cellular-based wireless communication networks. Such networks include various network nodes. The network nodes may include base stations which respectively provide coverage for a radio cell.
A user equipment of a mobile communication network may be a Proximity Service (ProSe) enabled device. Several ProSe enabled user equipments which are located in proximity to each other are operative to perform device-to-device (D2D) communication. D2D communication allows user equipments of a mobile communication network to directly communicate with each other when the user equipments are located in proximity to each other. D2D communication has a wide variety of applications, including public safety and other use cases. Emergency calls are one example for public safety use cases of D2D communication. For illustration, if a user equipment indicates an emergency call situation, another user equipment may provide repeater function to ensure good network coverage for the user equipment. Direct data or voice communication between user equipments is another example for use cases of D2D communication. For illustration, ProSe enabled user equipments located in proximity to each other may engage in data or voice communication. The respective D2D communication is not transmitted to the radio access network of the mobile communication network.
In order to perform D2D communication, a user equipment must be capable of detecting one or several other user equipments which are located in proximity to the user equipment. The resources, e.g. the subcarrier frequencies, slots and/or symbols which the user equipment may use for the device-to-device discovery may be allocated to the user equipment by a base station. The base station may allocate resources for the device-to-device discovery and/or for the device-to-device communication by broadcasting system information or by performing a Radio Resource Control, RRC, signaling, for example.
It may be required that the resource allocation is changed. For illustration, when the number of user equipments in the coverage area of a base station increases, it may be desired to adapt the resources allocated for the device-to-device discovery and/or for the device-to-device communication to ensure that the device-to-device discovery and/or the device-to-device communication does not severely affect the communication between the user equipments and the radio access network. It is a challenge to inform the user equipment(s) of a change in resource allocation in an efficient way. For illustration, if the information on the change in resource allocation were always transmitted in a system information block message, the system information block message would be processed also by user equipments which are not ProSe-enabled, causing processing overheads. If the information on the change in resource allocation were transmitted in RRC signaling, this would increase the traffic load on the air interface of the radio access network.